Methane

state at 25 degrees Celsius

Methane is used as feed stock to chemical industry and is the main constituent of the fuel natural gas. Chemical, physical and thermal properties of methane: Values are given for gas phase at 25 °C /77 °F / 298 K and 1 atm., if not other phase, temperature or pressure given.

The most plausible answer is b, duration. the given amount of time is considered how long it last for.

Ok so co(g) is not pronoused that. the only clue is that youpronouse it the oppisote way.